Multi-energies assisted and all-weather recovery of crude oil by superhydrophobic melamine sponge

Superhydrophobic Photothermal Halloysite-Based Sponge for Oil-Water Separation and Fast Recovery of High-Viscosity Crude Oil Spill

Frequent oil spills and oily water pose a severe threat to ecosystems. Besides, efficient cleanup and recovery of high-viscosity marine crude oil remain a global challenge. Herein, a superhydrophobic halloysite-based oil-adsorption sponge (k-HNTs@MS2) with a photothermal conversion property was fabricated via a one-step calcination technique and a dip-coating method. Briefly, melamine sponges (MS) were calcined in argon and then dip-coated with halloysite nanotubes (HNTs) modified with 3-aminopropyltriethoxysilane (KH-550) in a PDMS/n-hexane solution. Due to the three-dimensional porous skeleton structure of the sponge and the low surface energy coating on the surface, the as-prepared k-HNTs@MS2-1 exhibited outstanding superhydrophobicity (WCA > 155°), high oil absorption capacity (18.4-37.0 g g-1), and excellent separation efficiency (>99.2%) for various oil-water mixtures. Notably, the modified sponge can use the photothermal effect to rapidly heat up and reduce the viscosity of crude oil. This enabled k-HNTs@MS2-1 to absorb more than 8 times its own weight (8.9 g g-1) of crude oil under simulated sunlight illumination of 1.0 sun (1.0 kW m-2). This work might offer a multifunctional solution for oil-water separation and cleaning up large-area viscous crude oil spills, leveraging the unique combination of superhydrophobicity, high oil absorption capacity, and photothermal conversion properties.

Lignin Microsphere/TiO2 Composite-Based Melamine Sponge with Superhydrophobic and Photothermal Properties for Oil/Water Separation and Anti-Icing

Frequent oil spills and the discharge of oily wastewaters have caused a serious threat to the environment, ecological systems, and the health of human beings. Herein, a durable photothermal and superhydrophobic melamine sponge has been prepared by decorating lignin microspheres (LMs) and TiO2 nanoparticles via the self-polymerization of dopamine. The superhydrophobic sponge shows excellent chemical stability, thermal stability, mechanical durability, and recyclability. The adsorption capacities of the superhydrophobic sponge for oils and organic solvents range from 22.4 to 84.2 g/g, showing high separation efficiencies larger than 98.6% after 15 cyclic tests. Due to the photothermal effect, the maximum surface temperature of the superhydrophobic sponge reaches 65.2 °C under solar irradiation (1 sun), and the superhydrophobic sponge successfully achieves the ice-free property at a low temperature of -17.8 °C under solar irradiation (0.5 sun). Besides, the LMs@TiO2 composite coating can be employed on several substrates (i.e., filter paper, carbon cloth, steel mesh, Al sheet, Cu sheet, and NdFeB) to realize surface superhydrophobicity, and exhibits excellent anticorrosion for the coated NdFeB. Therefore, this study proposes a low-cost and multifunctional superhydrophobic MS, opening a new avenue to the rational design of superhydrophobic MS for applications in oil/water separation, anti-icing, and anticorrosion.

Oil recovery and heat transfer performance of polyurethane sponges coated with 3D carbon nano networks

Heatable super hydrophobic polyurethane (PU) sponges (S-GNS/CNT/PVA@PU) containing three-dimensional (3D) carbon nano-networks (CNNs) coatings made from two-dimensional (2D) expanded graphite nano-sheets (GNS) bridged by one-dimensional (1D) carbon nano-tubes (CNT) were constructed using polyvinyl alcohol (PVA) as binder, in which light and/or electric energy could be rapidly converted into heat to reduce the viscosity of spilled heavy oils, resulting in greatly increased oil. Their heavy oil recovery rate could reach 792 kg/(m2·h) under combined light and Joule heating of 1 sun and 5 V. Surface heat dissipating coefficient Ks, heat dissipating index n, and surface heat absorption capacity Cs were studied relating to sizes and shapes of surface heating fields under varied heating modes. Deviations from Newton's law of cooling were observed, with n values varying from 1.070 to 1.690.

Superhydrophobic Co-MOF-based sponge for efficient oil-water separation utilizing photothermal effect

Effectively addressing crude oil spills remains a global challenge due to its high viscosity and limited flow characteristics. In this study, we successfully prepared a modified sponge (PCP@MS) by embedding the photothermal material of Co-HHTP and coating the melamine sponge (MS) with low-surface-energy polydimethylsiloxane (PDMS). The PCP@MS exhibited outstanding hydrophobicity with WCA of 160.2° and high oil absorption capacity of 59-107 g/g. The PCP@MS showed high separation efficiency of 99.2% for various oil-water mixtures, along with notable self-cleaning properties and mechanical stability. The internal micro-nano hierarchical structure on the sponge surface significantly enhanced light absorption, synergizing with the photo-thermal conversion properties of Co-HHTP, enabled PCP@MS to achieve a surface temperature of 109.2 °C under 1.0 solar light within 300 s. With the aid of solar radiation, PCP@MS is able to heat up quickly and successfully lowering the viscosity of the surrounding crude oil, resulting in an oil recovery rate of 8.76 g/min. Density functional theory (DFT) calculation results revealed that Co-HHTP featured a zero-gap band structure, rendering advantageous electronic properties for full-wavelength light absorption. This in situ solar-heated absorbent design is poised to advance the practical application of viscous oil spill cleanup and recovery.

Recent advances in functional micro/nanomaterials for removal of crude oil via thermal effects

Crude oil is one of the most widely used energy and industrial raw materials that is crucial to the world economy, and is used to produce various petroleum products. However, crude oil often spills during extraction, transportation and use, causing negative impacts on the environment. Thus, there is a high demand for products to remediate leaked crude oil. Among them, oleophilic and hydrophobic adsorbents can absorb crude oil through thermal effects and are research hotspots. In this review, we first present an overview of wettability theory, the heating principles of various thermal effects, and the theory of reducing crude oil viscosity by heating. Then we discuss adsorbents based on different heating methods including the photothermal effect, Joule heating effect, alternating magnetic field heating effect, and composite heating effect. Preparation methods and oil adsorption performance of adsorbents are summarized. Finally, the advantages and disadvantages of various heating methods are briefly summarized, as well as the prospects for future research.

Molecular insights into the adsorption and penetration of oil droplets on hydrophobic membrane in membrane distillation

Membrane fouling induced by oily substances significantly constrains membrane distillation performance in treating hypersaline oily wastewater. Overcoming this challenge necessitates a heightened fundamental understanding of the oil fouling phenomenon. Herein, the adsorption and penetration mechanism of oil droplets on hydrophobic membranes in membrane distillation process was investigated at the molecular level. Our results demonstrated that the adsorption and penetration of oil droplets were divided into four stages, including the free stage, contact stage, spreading stage, and equilibrium stage. Due to the extensive non-polar surface distribution of the polytetrafluoroethylene (PTFE) membrane (comprising 95.41 %), the interaction between oil molecules and PTFE was primarily governed by van der Waals interaction. Continuous oil droplet membrane fouling model revealed that the new oil droplet molecules preferred to penetrate into membrane pores where oil droplets already existed. The penetration of resin (a component of medium-quality oil droplets) onto PTFE membrane pores required the "pre-paving" of light crude oil. Finally, the ΔE quantitative structure-activity relationships (QSAR) models were developed to evaluate the penetration mechanism of pollutant molecules on the PTFE membrane. This research provides new insights for improving sustainable membrane distillation technologies in treating saline oily wastewater.

Recent progress in magnetic polydopamine composites for pollutant removal in wastewater treatment

Various water pollution issues pose a significant threat to human water safety. Magnetic polydopamine composites (MPCs), which can be separated by magnetic fields after the adsorption process, exhibit outstanding adsorption capacity and heterogeneous catalytic properties, making them promising materials for water treatment applications. In particular, by modifying the polydopamine (PDA) coating, MPCs can acquire enhanced high reactivity, antibacterial properties, and biocompatibility. This also provides an attractive platform for further fabrication of hybrid materials with specific adsorption, catalytic, antibacterial, and water-oil separation capabilities. To systematically provide the background knowledge and recent research advances in MPCs, this paper presents a critical review of MPCs for water treatment in terms of both structure and mechanisms of effect in applications. Firstly, the impact of different PDA positions within the composite structure is investigated to summarize the optimization of properties contributed by PDA when acting as the shell, core, or bridge. The roles of various secondary modifications of magnetic materials by PDA in addressing water pollution problems are explored. It is anticipated that this work will be a stimulus for further research and development of magnetic composite materials with real-world application potential.

Joule Heating-Assisted Crude Oil Purification by a Poly(pyrrole)-Modified Microfibril Cellulose Membrane

Using membrane materials to purify viscous watery oil from industrial production processes and accidental oil spills is of great importance but still challenging. Based on the excellent electrical conductivity and electric-thermal conversion of poly(pyrrole) (PPy), a hydrophobic PPy-modified micro-fibrillated cellulose membrane (P-CP) was successfully prepared. The size of the P-CP membrane can be customized to meet specific requirements. In this research, the membrane diameter is capable of reaching 24 cm. By applying a voltage ranging from 0 to 12 V, the surface temperature of the P-CP membrane can be elevated to roughly 120 °C. After 10 cycles of heating and cooling under 12 V voltage, the electric-thermal curves, surface hydrophobicity, and pore structure of P-CP membrane can remain stable, which suggests remarkable electric-thermal stability and reliability despite prolonged operation. The P-CP membrane shows good linearity between voltage and current (R2 = 0.997) and easy temperature control from room temperature to ∼120 °C at low supply voltage (0-12 V). Under the condition of 12 V power supply and self-gravity, the separation flux of the P-CP membrane for water-in-oil (W/O) emulsions (kerosene, diesel) is 2-3 times higher than that at room temperature, and the separation efficiency is also improved. Importantly, the P-CP membrane shows excellent separation performance for high viscosity water-in-crude oil emulsions, with a separation flux of 40 L m-2 h-1 by gravity. Compared to the situation without electricity, the separation flux of water-in-crude oil emulsion has increased four-fold. The joule heating of the P-CP membrane expands its service time and application scenarios, demonstrating its great application prospects in actual viscous oil-water emulsion separation.

TDA/rGO@WS with Joule heat and photothermal synergistic effect: A promising adsorption material for all-weather recovery of viscous oil spills at sea

Oil spills are a global environmental protection challenge, and traditional adsorption materials have poor effect on low temperature and high viscosity marine oil spills. This article reports composite adsorption materials TDA/rGO@WS for viscous oil spills: loaded with rGO/TDA coating on a commercial biomass wood pulp sponge (WS), achieving Joule heating, photothermal effect and hydrophobic modification. The results showed that the TDA/rGO@WS has good photothermal conversion ability and Joule heating ability, and the temperature increased to 83.7 °C and 148 °C, respectively, under simulated solar irradiation and additional voltage at room temperature. The efficiency of adsorption at a low temperature of 5 °C increased by 22.41% at 1 sun and by 51.53% at 10 V. Temperature effectively reduced the viscosity of the offshore oil spill and ensures the efficient adsorption of oil spills at low temperatures promoted. The TDA/rGO@WS also showed good hydrophobicity (WCA=129°), excellent efficiency of water-oil separation (99.53%) and good adsorption capacity (9.4-13.68 g/g) for marine fuel oils. TDA/rGO@WS effectively solves the problem of cleaning up high-viscosity oil spills from ships in winter and polar waters, and proposes a new strategy for all-weather efficient treatment of oil spills at sea.

Hydrophobic organogel sorbent and its coated porous substrates for efficient oil/water emulsion separation and effective spilled oil remediation

Frequent offshore oil leakage accidents and large quantities of oily-wastewater produced in industry and daily life bring huge challenges to global water purification. The adaptability and stability of organogels as adsorbent materials have shown wide application prospects in the field of oil-water separation. Herein, the organogels displayed stable hydrophobic/lipophilic properties with high absorption ability (1200 wt./wt%), efficient sorption of multiple emulsions (>99.0%), and good reusability. More importantly, the organogels were successfully assembled with 2D/3D substrates to achieve excellent sorption capacity (102.5 g/g) and recycling performance (50 cycles). The gel-carbon black assembled on MS (GCB-MS) sorbent with excellent photothermal conversion performance, and can rapidly heat the surface to 70.4 °C under 1.0 sunlight radiation (1.0 kW/m2) and achieved an ultra-high sorption capacity of about 103 g/g for viscous crude oil. Meanwhile, the GCB-MS was combined with a pump to build continuous oil spill cleaning equipment to achieve a super-fast cleanup rate of 6.83 g/min. The developed hydrophobic organogels had been expanded unprecedentedly to realize the comprehensive treatment of oily-wastewater in complex environments, including layered oils, emulsions, and viscous crude oil spill, which provided an effective path for the comprehensive treatment of oily wastewater in complex environments.

Melt-blown fiber felt for efficient all-weather recovery of viscous oil spills by Joule heating and photothermal effect

Adsorbents play a vital role in responding to marine oil spills, yet effectively cleaning up viscous oil spills remains a technical challenge. Herein, we present a superhydrophobic oil-adsorbing felt prepared using melt-blown technology and functionally enhanced with a photoelectric composite CNT/PANI coating for effectively cleaning up high-viscosity oil spills. By virtue of its superior solar/Joule heating ability and thermally conductive fiber network, p-CNT/PANI@PP notably reduced crude oil viscosity and enhanced the oil diffusion coefficient within pores. Leveraging primarily solar heating and supplemented by Joule heating, p-CNT/PANI@PP demonstrates an impressive in-situ adsorption rate of up to 560 g/h for ultra-high-viscosity crude oil (c.a. 138000 mPa·s), alongside an adsorption capacity of 15.57 g/g. This measure enables efficient viscosity reduction and continuous day-and-night recovery of viscous crude oil, addressing the challenges posed by seasonal fluctuations in seawater temperature and adverse weather conditions. Moreover, a conveyorized collector integrated with an oil-adsorbing felt realizes continuous recovery of viscous oil spills with speed control to tackle varying thicknesses of oil film. Given the top-down material design, superior functionality, and applicability to applications, this work provides a comprehensive and feasible solution to catastrophic large-area viscous oil spills.

MXene/Graphene modified cellulose aerogel for photo-electro-assisted all-weather cleanup of high-viscous crude oil from spill

The frequent occurrence of oil spills has led to serious environmental pollution and ecological issues. Given the high-viscosity of crude oil, it is essential to develop sorbents with efficient viscosity reduction and sorption capacity in various environmental conditions. Herein, a superhydrophobic carboxymethyl cellulose (CMC) aerogel co-modified by MXene and graphene jointly (M-Mxene/Gr CA) with aligned channels structure was prepared. The aligned channels structure can effectively improve the longitudinal thermal conductivity and reduce the sorption resistance. Through the modification of MXene and graphene, the aerogel realized efficient photo/electro-thermal conversion, thus ensuring its adaption to various working environments. The rapid heat generation can significantly reduce the viscosity of crude oil, achieving rapid recovery. Under one sun illumination (1.0 kW/m2), the surface temperature of M-Mxene/Gr CA can reach 72.6 °C and its sorption capability for high-viscous crude oil reaches 18 g/g. Combining photo-thermal and electro-thermal (0.5 kW/m2 and 23 V), the average sorption rate of crude oil can reach 1.3 × 107 g m-3 s-1. Finally, we present a continuous sorption system to recover offshore oil spills under the assistance of a pump. This work provides a new option for tackling high-viscous offshore oil spills due to its environmental friendliness and fast sorption capacity.

Coupling Carbon-Based Composite Phase Change Materials with a Polyurethane Sponge for Sustained and Efficient Solar-Driven Cleanup of Viscous Crude Oil Spill

The efficient cleanup of crude oil spills is a worldwide problem due to their high viscosity and low fluidity. Under the assistance of solar radiation, adsorbents with in situ heating function are becoming the ideal candidates to solve this problem. In this study, a new strategy coupling a polyurethane (PU) sponge with phase change materials (PCMs) is proposed to realize the efficient utilization of solar energy and crude oil cleanup. Wormlike carbon nanotubes/mesoporous carbon (CNTs/MC) with a core-shell structure was used to encapsulate polyethylene glycol (PEG), which was then introduced into the PU sponge for photothermal conversion and thermal storage. After coating with a polydimethylsiloxane (PDMS) layer, the sponge was further endowed with hydrophobic characteristics. Additionally, PDMS can function as a binder between PEG@CNTs/MC and sponge skeleton. The resulting PEG@CNTs/MC/PU/PDMS (named as PEG@CMPP) exhibited excellent photothermal conversion and high absorption capacity for high-viscosity crude oil. Most importantly, thanks to the heat storage properties of PEG, the stored heat can be sustainably transferred to the surrounding crude oil to promote its continuous absorption even under insufficient light intensity conditions. The crude oil absorption capacity of PEG@CMPP-3 reached approximately 0.96 g/cm3 even after the light source was removed, which manifested the distinctive advantages compared to the conventional photothermal adsorbent. The proposed approach integrates the high efficiency of solar-assisted heating and energy-conserving advantage, thereby providing a feasible strategy for highly efficient remediation of viscous crude oil spills.